That if a bishop shall possess a diocese which he has
snatched from heresy for three years, no one may take it from him.

Item, it seemed good that if
anyone after the laws should convert any place to Catholic unity and
retain it for three years without opposition, it should not be taken
away from him afterwards. If however there was during those three
years a bishop who could claim it and was silent, he shall lose the
opportunity. But if there was no bishop, no prejudice shall
happen to the see,482482 In the Latin
“Matrici.” but it shall be
lawful when the place that had none shall receive a bishop, to make the
claim within three years of that day. Item, if a Donatist bishop
shall be converted to the Catholic party, the time that has elapsed
shall not count against him, but from the day of his conversion for
three years he shall have the right of making a claim on the places
which belonged to his See.

Notes.

Ancient Epitome of Canon
CXIX.

Whosoever shall convert a region to Orthodoxy and
shall keep it converted for three years, let him be without
blame. But if the bishop converted from Donatus within three
years of its conversion seeks his diocese again, let it be returned to
him (εἰ
ἐνάγει, ἐναγέτω.)